When to Plant Radishes in Ontario
Published: April 24, 2026 · Updated: April 27, 2026
The fastest crop in the garden — ready in 22–30 days. Direct sow 4–6 weeks before last frost and succession plant every 2 weeks for a continuous spring harvest.
Radishes grow well in this province with appropriate variety selection and standard Canadian planting timing.
Radishes Planting Window for Ontario
Direct sow outdoors: March 16–26
Minimum soil temperature: 4°C (40°F)
Days to harvest: 22–30 days
Sun requirement: Full sun to partial shade
Fall crop planting: September 27–October 7
⚠ Direct sow radishes 4–6 weeks before last frost — one of the fastest crops in the garden. Ready in as little as 22 days. Succession plant every 2 weeks for continuous harvest.
Ontario Cities — Radishes Planting Dates
City-specific frost dates and radish planting windows for Ontario.
Growing Radishes in Ontario
- Thin to 2-inch spacing when seedlings are an inch tall — crowded radishes produce small woody roots.
- Succession plant every 10–14 days from early spring through late spring for continuous harvest.
- Plant as a row marker for slow-germinating crops like carrots — radishes sprout in days and mark the rows.
- Harvest promptly at target size; over-mature radishes turn pithy, woody, and unpleasantly hot.
Companion Planting for Radishes
In Ontario gardens, pair radish with Lettuce, Carrot, Pea, Cucumber. Avoid planting near Hyssop, Grape, which compete with or inhibit radish growth.
Common Pests and Problems
Radishes in Ontario are commonly affected by Flea Beetle, Cabbage Root Maggot, Aphid. Floating row covers installed at planting block most adult pests from laying eggs, and a weekly scouting routine catches infestations before they damage the crop.
Frequently Asked Questions
When should I plant radish in Ontario?
In Ontario (Canadian Zones 5b–6b), direct sow radish around March 16. Radishes grow well in this province with appropriate variety selection and standard Canadian planting timing.
What is the best radish variety for Ontario?
Ontario gardeners should prioritise varieties bred for shorter seasons or Canadian climates. For radishes in Canadian Zones 5b–6b, look for cultivars labelled under 30 days to maturity. Local nurseries and provincial seed exchanges curate varieties that ripen within Canadian frost-free windows.
How does Ontario's climate affect radish?
Ontario spans Canadian Zones 5b–6b with frost-free seasons ranging from roughly 153 to 195 days. Radishes actually prefer the cooler spring and fall windows typical of Ontario, making them one of the most reliable crops in the province.
Can I grow radish in containers in Ontario?
Yes. Container growing on balconies and patios extends the viable growing area across every Canadian province. Dark-coloured containers warm up faster in spring and extend the season on both ends. Choose a 5-gallon or larger pot for radish and water daily during hot summer weather, since containers dry out quickly.
When is the first fall frost in Ontario?
First fall frost dates in Ontario range from October 15 in the coldest areas to November 1 in the warmest. For a fall radish crop, count back from your local first-frost date and plant around September 27–October 7.